Measurement or variation of physical states of materials



Jano 25p 1949- M. K. TAYLQR ET AL. 460B? MEASUREMENT OR VARIATION OFPHYSICAL STATES OF MATERIALS 3 Sheeis-Sheei; l

Filed Oct. 2l, 1946 Jan. 25, 1949. M. K. TAYLOR ET Ax. 2,46099MEASUREMENT OR VARIATION OF PHYSICAL STATES OF MATERIALS 3 Sheets-Sheet2 Filed 00T.. 2l, 1946 Jan. 25, 1949.

M. K. TAYLOR ETAL 2,460,199 MEASUREMENT OR VARIATION OF PHYSICAL STATESOF MATERIALS Filed oct. 21, 194e 3 Sheets-Sheet 3 VOLTS VOLTS PatentedJan. 25, 1949 MEASUREMENT on VARIATION lor PHYSICAL STATES OF MATERIALSMaurice :Kenyon Taylor, Belmont, Scotland, and

Alfred DouglasA Knowle assignors to Ferranti L land, aiBritjish companyApplic'ationOctober 21, 1946, Serial No.

s, Chadderton, England, imited, Hollinwood, Eng- In `Great BritainOctober 1945 2 Claims. l

This invention relates to the variation of the physical state ofmaterials such as the dampness ofV cloth, Vand in particular toapparatus for achieving this Apurpose-by utilising the effect ofvariation of the physical state on a condenser of which the materialforms all or part of the dielectric.- p

The main object of* thepresent invention is to provide means forvaryingthe speed of travel of a continuous or longpiece ofthe materialthrough a. treatment zone. in Vwhich the physical characteristic to be'controlled'.is varied, the variation in speed being dependent uponvariation of the physical state from a required standard. For examplecloth maybe passed through a drying oven to control its humidity. If thecloth emerg- .ing fromthe` oven is too'damp the speed of the materialthrough the' oven will be decreased and vice versa. ...According .to thepresent invention a method ofvarying the physical state of a materialcomprises moving the material through an oven or other treatment zone,deriving a voltage which is proportional to thedampness or otherphysical stateof the material, said voltage being derived onlyl 'atpredetermined regular distances along the material, and positively ornegatively accelerating the motion of said material for periods ofacceleration proportional to the voltage so derived.

Thus in accordance with the invention the material is tested only atregularly spaced intervals and lthe speed of movement of the materialthrough the treatment zone is varied at similar intervals if thephysical state varies from the required value the variation of speedbeing in the required corrective direction and to a degree proportionaltothe degree of variation from the standard. The rate of variation ofthe speed may be constant, and the duration of this variation beingproportional over the control range to the degree of variation from thestandard.

An apparatus forcarrying out the invention may comprise means for movingthe material through an oven or 'other treatment zone, means forpositively and negatively accelerating the motion ofsaid'materlal,vo1tagederiving means for deriving a1 voltage which isproportional to the dampness or other physical state of the material,means for rendering the voltage-deriving distances along the material,`andy relay means @WP-11rd by the. derived. veltase so as *waccelil-Siigj @@1031 lesitivelr. .011 ,negatively 'for periods ofacceleration proportional to said voltage.

The derivation of periods of acceleration from and proportional to thedegree of said voltage may condenser whichr is periodically dischargedby means' of a gas-dis charge tube, which completes a relay circuit. Twosuch valve-and-tube circuits `maylbe provided ied with voltageof/opposite polarity and serving to initiate and stop the positive ornegative accelerations.

The movement of the 'material through the oven may be effected byanelectric motor"the speed of which can be altered by altering theposition of its brushes by means of a pilot motor controlled by therelay.

For rendering the current-deriving means operative only atpredetermined'intervals a 'commutator device may be provided. in thehightension lead to the valve whereby the 'high-'tem intervals, thespeed of the commutator.l being controlled so that the said intervalscorrespond with similar lengths oimaterial irrespective of the speed oftravel of the material.

A constructional form of the invention will now be described by way ofexample wtih reference to the Yaccompanying diagrammaticdrawings inwhich:

Figure l shows the electrical layout of an apparatus for derivingappropriate voltages;

Figure 2 shows the electrical layout of additional apparatus to be usedinconjunctionwith the apparatus shownin Figure l,.for controlling thespeed of cloth through an oven in accordance with the present invention;y

Figures 3 and 4. are graphs to be referredto; and

Figure 5 shows a detail to be described.V e

An oscillator triode Ill has its grid connected by a suitable gridleadIl to earth, this grid-lead having a by-pass condenser` l2 connectedacross it. The anode is connected to one plate of a iixed condenser i3,between the other plate of which and earth is a variable tuningcondenser I4. This condenser is motor operated and the condenser an-rlmotor will be hereinafter more fully described. The anode is .alsoconnected vto a position between two inductance coils l?, i3, `which arein series and the second of which is connected to"'oneV plate of la xedcondenser lathe. other plate ot which isv connected to. oneterminalof a3 switth 28 the other terminal of which is earthed. The switch 2t isoperated by a relay controlled by a commutator to be described later.The other coil is connected to one plate of a condenser 2l the otherplate of which is earthed, and it is also connected to a high-tensionsupply and by a choke coil 22 to the anode of a pentode amplifier valve2d the control grid of which is connected by a fixedY condenser 25 tothe triode cathode, the latter also being connected toearth through Vasuitable choke 25 and to one plate of another condenser 21 the otherplate of which is connected to the triode anode. rlhe cathode andcontrol grid of the pentode are also earthed through suitableresistances 2%, Sii respectively. The anode of the pentode` is connectedto one plate of a condenser 3i the other plate of which taneously movesover to contact 55.

is connected to earth through two inductance coils 32, 33, in series,which Vrare coupled respectively with inductance coils/,34, 3,5respectively in two tuned circuits. The standard circuit contains avariable resistance 3% and variable condenser 31 while the measuringcircuit contains the plates .t3V between which the material is .asscd,both circuits being earthed by lead 13S. rThe inductance coils 32, 33,are connected to the cathode of a diode detector valve d'2 the anode ofwhich is connected to the control grid of a second pentode valve G3 thecathode of which is earthed and between this anode connection and earthare a condenser iid and a resistance l5 in parallel. The 'second pentodeanode is fed with hightension current through a resistance 48 inparallel with a condenser t9, and is connected by a condenser t tothecontrol grid of a third pentode valve 5i, this grid being also earthedthrough a resistance 52; the cathode of valve 5i is earthed through aresistance. The lanode of the third pentode is connected through theprimary coil 53 Y, of a transformer to the high-tension supply, a

shunt resistance 513 being provided across this coil.'V The Vsecondary55 of this transformer has contact pointsj'i', 58, engaged alternatelyby a movable switch member 59 which is operated by a relay insynchronism with the switch 2i?. The mid-point of this secondary isearthed by a lead Gli so that, as will be more fully describedhereinafter, the opposite ends, 5l, 62, of the transformer are ofopposite polarity. The switch member 59 is `connected toa condenser Gwhich is earthed and in parallel with this condenser is a smoothingresistance 55 and condenser 58. A lead 51, between the smoothingresistance' and condenser, is taken to the device for controlling thephysical state of the material under test which is described'below. Theother grids of the pent-ode valves are provided with any normal conr.ons customary to their use as amplifying vr'fes. Leads 63, S9, areconnected to hightension supply-positive and negative respectively.

The construction and operation oi the parts M, 2G, and 59 is shown morefully in Figure 5. The condenser ill comprises a series of xed plates 1lwhich are quadrantal in shape and a series of movable plates 12 whichare earthed by a slip ring (not shown) and have a similar shape to thenxed plates. VThe movable plates are fitted on to a rotatable spindle 13and are symmetrically arranged so as to form two diametrically oppositesets. Rotation of the spindle is eectedby a small motor 11i.

The spindle 13 carries a commutator T55 which is composed of alternatequadrants of conducting and insulating material. The Vcornmutator isengaged by two brushes 4 8U, 8l, the former of which is connected to arelay 15, and the latter of which is earthed. Relay 1S controls switches25 and 5S; when the relay is not energised switch 2i) is open and switchmember 5S makes contact with contact 51; when the relay becomesenergised switch 2t closes and switch member 59 simul- By thisarrangement one set of plates 12 will move through approximately degreeswhilst the sec= ond inductance coil I8 and condenser i9 are includedinthe oscillator circuit thereby sweeping a frequency band whichincludes the resonai` frequency of the standard circuit and a pulse oi'negative polarity is taken from the contact 55 end of the transformersecondary 55; whereupon the commutator causes the relay 16 to openswitch 2) and reverse switch 59 so that the second inductance coil is nolonger included in the circuit and during the next 90 degreesoirevolution of the condenser plates a different frequency band willconsequently be swept which includes the resonant frequency of themeasuring circuit, and Va pulse of positive polarity is taken from 'thecon# tact 51 end of the transformer secondary.` During the next degreesof movement ofthe condenser plates the effect is repeated with the otherset of movable condenser plates. It is arranged that the tuning-condenser is at a maximum or minimum value when the second inductancecoil is switched in or out of the oscillator circuit so that eachfrequency band is covered in one direction. Y

In the arrangement described above voltages are derived from both thestandard and measuring circuits which are amplitude modulated by theloscillations supplied by the oscillator. The amplitude in each tunedcircuit is a' maximum Y when the oscillator frequency coincides with theresonant frequency of rthe tuned circuit. These voltagesare applied to adiode rectifier to effect demodulation. The resultant signal has apulsatory wave form which is amplied by the second pentode after whichthe pulses from one circuit are made negative and the pulses fromtheother circuit are made positive by means -oi the changeover switch 59with a View to adding them in order to obtain the arithmeticaldifference. For this purpose the pulses are applied to the grid of thepentode valve in the anode lead or" whichis the transformer 53, 55thesecondary coil of which as already described has its centre pointvconnected to earth so that pulsesof opposite polarity derived from thetwo tuned circuits are developed across that` half of the secondarybrought into action by switch 59. The condenser accordingly receivesalternate positive and Ynegative charges.v The pulses ar-e smoothed bymeans oi the condenser 66 and resistance G5, thereby giving a D. C.level of voltage corresponding to thefdifference in the magnitude of thepulses; v

if the iinal output difference isl negativerthe Q value of the measuringcircuit is too snlall and the material is too wet. Iii thevoltagediiference is positive the Q value of the measuring circuit istoo large and the material is too dry. If the voltage is Zero the two Qvalues lare the same and the material has therequirecl moisturecontent.V l Y d Y Y The apparatus so vfar described comprises thesubject of co-pending British patent application No. 28,177 ofV i945 inwhich itis more fully described. f .Y n u Y For the purposeof .thefpresent invention the additional apparatus shown in Figure 2 is providedin which. 55 the. sametransformer .Secondary coil as is shown in Figurel, andthe switch 59, contacts 513,158, condensenG-fl, `resistance-65,.condenser 66,- and output lead 61, `also represent the same parts as areindicated by the same numerals in Figure l. Y e

The voltage across condenser 66 is proportional to the deviationin`wetness ofv the4 material .from therstandard. lfgthe `material is toodry this voltage is positive whileif lth s yoltageis negative thematerial is too wet. o Y i f y Anothervoltage is obtained by a lead 80(taking the place of the lead 60) from the centre tapping point of thecoil 55,;this voitagebeing smoothed byrcondenser 8|. andresistance82.vAcondenser 83 is also provided corresponding.- to the condenser 68.[The nvoltagesacross condensers 66 and 03 are therefore equal but ofopposite polarity. Thus if `the original voltage across condenser 69 isillustrated by the graph Figure 3, the voltage across condenser 83 willbe as illustrated by Figure 4. Y

These voltages are applied respectively to separate similar circuits.The ilrst of these circuits includes a pentode valve 86 to the controlgrid of which the lead 61 is connectedf The cathode of the valve isconnected by way of a resistance 90 to the earthed negative pole of ahigh-tension supply. In the lanode leadof the pentode valve are acondenser 81 anda resistance 88 in parallel; the anode side of condenser81 is connected to the cathode of a gas-discharge'tube 9|; the otherside oi the condenserv is connected to the positive pole of thehigh-tension supply and` to one end of an energising coil A92 the otherend-'of which is connected to the travelling contact oi a single-poledouble-throw switch 93,V OneXed contact 93A of this switch is connected'tothe 'anode of the gas-discharge tube 9| and the other iixed contact93B is connected to earth through another energising coil 94 the purposeof which will be described later. The second of theafo'resaid twocircuits comprises similarly connected valve 96, condenser 91,resistances 98 and |00, gas-discharge tube coil |02, switchm |03, andcoil |04.` The coil 92 actuates the switch 93.` 'When coil 92 is notenergisedthe travelling contact rests on contact 93A; when energised thetravelling contact moves to contact 93B and is there held on till thecircuit external to the relay is broken, as will be described later.Coil |02 actuates the switch |03 in like manner to connect |02alternatively to the anode of the gas-discharge tube |0| in the othercircuit by way of :fixed contact |03A or to coil |04 by way of xedcontact 503B.

The current through each of the pentode valves varies according to thepotential applied to the grid. The condenser in the anode lead is thuscharged at a rate which depends on the current and consequently on thepotential applied to the grid, this potential being proportional overthe working range of the apparatus to the degree of variation of thedampness of the cloth from the standard. If the voltage applied to thegrid is positive the condenser charges up quickly but if this voltage isnegative a comparatively long period is required to charge thecondenser. The condenser charges up until the plates reach the potentialof the striking voltage of the gas-discharge tube which accordinglybecomes conducting thereby completing a circuit through 92, the tube 9|,and switch 93 (by contact 93A). Thereupon, coil 92 being energised,switch 93 operates and completes a circuit from the` positivehightension supply through 92, 93 (by contact 93B), and 94 to thenegative high-tension pole, thereby energising coil 94. Hence the timetaken to complete the latter circuit depends on the timeat which the gastube flashes. If a large positive voltage (indicating too dry material)is applied to the grid of the pentode 86 the coil 94 is energised almostimmediately; if a small positive voltage is applied to the grid, switch93 will not move as soon; and if a negative voltage, indicating too wetmaterial) is applied to the grid, switch 93 will not move until after acomparatively long period. The other circuit behaves similarly exceptthat/since the current input to its pentode valve 96 is of oppositephase, quick energisation of coil |04 indicates too wet material andslow energisation too dry material.

' The coils 94, |04, actuate two'relay switches |06, |01, respectively.Switch |06 has four contact points, Hi, H2, H3, H4, and switch |01 alsohas four contact points H5, H9, H1, H8, Points H2, H3, H5, H8, are allconnected together electrically in a permanent manner. Contacts H4 andH1 are also connected together and to one lead from the supply for thewindings of a split rleld pilot motor |20. Contacts and I6 arerespectively connected to the ends of the two iield windings oi themotor, the common point of the windings being connected to the othersupply lead. The pilot motor drives a toothed member |2| which carriesthe brushes of the main motor !4 which in turn drives a roller |23 thatconveys the material |24 through an oven |25 that contains thetestingcondenser 38 offFigure l. The contact Hl is connected to that eldwinding of the pilot motor which effects an increase in the speed of themain'motor while contact |6 is connected to that winding which eiects adecrease in the speed of the main motor. The contacts l I3. H4, and l1,H8, vare connected by the movable contacts oi relays 94 and 04 whenthese relays are not energised and then there is no current to the pilotmotor so that the main motor speed is unaltered, When relay 94 isenergised its movable contact connects contacts III, H2, instead ofcontacts H3, H4, and 'when relay |04 is energised its movable contactconnects contacts H5, H6, instead of contacts H1, H8.

If for example the cloth is very dry a large positive voltage is appliedto the grid of the pentode associated with relay 94 so that the movablecontact of switch |06 will change from contacts H3, H4, to contacts H|,H2 almost immediately. The iield winding current of the pilot motor thenhas a path through contacts H1, |8, and contacts |H, H2, and operatesthe pilot motor to accelerate the main motor so that the cloth passesmore quickly through the oven and does not get so dry. At the same timea large negative voltage is applied to the grid of the pentode 96 andthe movable contact of switch |01 therefore changes at a later time fromcontacts H1, H8, to contacts H5, H6. The contacts H3, H4, and H1, H8,are now both open so that current controlling the relay has no outletpath and the motor therefore stays at its altered speed. The motor istherefore positively or negatively accelerated in the period between theoperation of the switches |06 and |01, andthis period is approximatelyproportional to the degree of variation of the dampness from thestandard.

The speed of the motor is not continuously varied but variation iseffected at intervals corresponding to intervals of distance along thecloth Yat which periodic tests are made. 'Ifhus upon making a test onone part of the clothl adjacent to the outlet end of the oven i. e., ifthe condenser 3S is located at the outlet end of the' oven, the speed ofthe next length of cloth (equal to the length of the oven) is alteredaccording to the degree ofdeviation of that part from the requiredstandard of humidity. This is effected as follows. In the high-tensionlead |28 to thev pentode anodes is a disc 29 of insulating materialwhich is rotated by geared connection to the main motor so that the discmakes one revolution in the period during which one position on thecloth travels the length of the oven. As the speed of the motor altersso does the speed of thisdisc. At one position on the circumference Y ofthis disc is a small piece |30 of conducting ma terial. As the discrotates high-tensionV current is applied to the valves through thisconducting piece once for a short period during each revolu-` tion ofthe disc. The valves are therefore only effective during these shortperiods and consequently only at 'these intervals is the test made on asmall part of the cloth and the speed of the motor altered accordingly.This disconnection of the high-tension supply at the end of each shortperiod de-energises the coils of relays 92 and lH12 thus causing them torestore, i. e. the travelling contacts to Vmove from fixed contacts 93Band 103B to xed contacts 93A and 103A respectively.

The main motor 14 also drives the switch 20, condenser I4, and switch59, so that the operation of these partsk is suitably related to theVoperation ofthe disc |29.

Should it he desired to eiect control more frequently than the llengthof the oven allows, the condenser plates between which the cloth passesfor test'purposes are placed nearer to the point of entry of the clothinto the oven. By this arrangement allowance is made for drying Subsc-'-quent to the measuring position. The length of cloth over whichcorrection is made at corresponding intervals is that between the startof the oven and the measuring position.

AWe claim:

1. An apparatus for controlling the movement of material in accordanceVwith variations inthe 8 physical state thereof comprising means formoving the material relative to a treatment zone, means for positivelyand negatively accelerating the motion of said material, voltagederiving 1 means for deriving two control voltages one of which ispositive, and the other of which is negative according to the directionof deviation from a standard and each of which is proportional to thedampness or other physical state of the mai6" terial, means forrendering the voltage deriving means operative only at predeterminedregular distances along the material, a pair of condensers adapted to becharged at-rates dependent on the polarities and potentials of saidcontrol voltages 15' respectively, means for discharging the condenserswhen predetermined potentials are reached, and relay means operated bythe discharging current and controlling the operation of saidaccelerating means lso as to accelerate said motion positivelyAandrnegatively according to which of the condensers discharges first,said relay means being also operated to stop the acceleration when theother condenser discharges, whereby the period of positive or negativeacceleration is pro- 2'5 portional to the period between discharging ofthe two condensers.

l 2. An apparatus as claimed in claim 1 wherein said control voltagesare respectively applied to the grids of two valves the current through30 which varies according to said voltage, and the anodes ofthe valvesare connected respectively to the condensers which are periodicallydischarged by means of gas-discharge tubes which complete relaycircuits.

35 l YMAURICE KENYON TAYLOR.

ALFRED DOUGLAS KNOWLES.

REFERENCES CITED The following references are of record in the o file ofthis patent:

UNITED sTATEs PATENTS Lnja et ai sept. 19, 1944

